IE54009B1 - Process and device for detecting foreign bodies in a liquid - Google Patents

Abstract

The invention relates to a process and device for detecting foreign bodies in a liquid, wherein the image of the apparent surface of the liquid in rotation in the immobilized recipients is formed, by reflection, diffraction, refraction or attenuation of the light coming from a source, on a matrix of reception and read cells. In the matrix each cell is perfectly delimited and its position is identified by numerization. A series of images is produced, of which a certain number are taken as reference and memorized. Each image is digitized and those images following the last memorized image is compared therewith cell by cell by a subtractor. The results of such a subtraction are compared with a threshold and results overstepping the threshold involve delivering a signal to a processor which controls a sort device arranged to eliminate undesirable units.

Description

The present invention relates to a process and a device for detecting foreign bodies, particularly solids, in a liquid and more especially to such process an-Ί device making possible automatic, rapid and reliable detection of the foreign bodies, such ac solid particles or defects, present in a liquid contained in a recipient, transparent to the mode of detection, and undesirable above a predetermined apparent size, whatever their shape and nature.

The invention therefore generally relates to a process and device for non-destructive control, which may be carried out even after definitive closure of the recipient with a view to marketing it, and, in the following specification, the invention will be set forth with reference to the non-destructive control of pharmaceutical products such as ampoules and/or bottles of injectable products, without, however, being limited to this application which is given only by way of particular example.

In fact, it is known that injectable liquids presented in ampoules and/or bottles must be subjected to strict controls, with the particular object of detecting, after the ampoules or bottles have been sealed, the presence of defects of very varied nature, form and dimensions : textile filaments (coming from clothing, filters, the atmosphere), granular particles, particles of glass or resulting from crystallization, dust, etc... The purpose of this detection is to allow recipients containing inadmissible defects to be eliminated. 4 0 0 8 To this end, it has already been proposed to control ampoules of injectable products by carrying out a process consisting in placing an ampoule in movement, for example in driving it in rotation on itself about its longitudinal axis, then in immobilizing it suddenly in order to develop in the immobilized ampoule a substantially circular movement of the contents thereof.

The useful surface of the ampoule defined by its width (corresponding to its diameter, in the majority of cases) andthe height of the liquid that it contains, is then scanned by a conventional television camera of analog type, and successive images thus obtained are compared, this enabling the presence of the particles contained in the liquid to be detected, reducing the risks of errors connected with the possible immobile and constant sources of parasitic signal, such as for example a defect in the material in which the ampoule is made, and/or a mark made on the ampoule.

However, the micro-instabilities in read-out of the ;>0 images, inherent to analog scanning, are the cause of mediocre functioning, as the position of the zone scanned at each instant is determined by two variable electrical voltages, one defining the horizontal position (x-axis) and the other the vertical position (y-axis). As these voltages are continually variable and as each point of the image is not physically or mechanically defined, this results in a slight apparent difference in position of the image of the same point, from one read-out to the next, and therefore a fixed object, such as a letter or part of letter printed on the ampoule, is considered as mobile and consequently assimilated to a foreign body, when two successive images are compared with each other.

Such a detecting device therefore creates artificial defects per se and leads to numerous errors in detection, which renders use thereof incompatible with the reliability required in particular in the pharmaceutical domain.

Moreover to proceed to comparisons according to an analog process involves instabilities which might be the cause of false rejections.

Patent Application Nos. FR-A-2 390 709 and 2 451 043 disclose detecting the presense of foreign matter in liquids by means of processes and apparatus enabling a zone of small area of the ampoule to be scanned. The ampoule, which is immobilized and whose contents are taken along in a pseudo-circular movement, as explained hereinabove, is interposed between a source fo light, for which the ampoule is transparent, and a photodeteetor device, the axis of the source of light being common or at least very close to and substantially parallel to the optical axis of the photodetector device. The variation in light, resulting from passage in front of this zone of small area, of a foreign particle suspended in the liquid, and driven in rotation therewith in its pseudocircular movement, enables it to be detected. This process of detection by occultation, since foreign bodies and 4 0 0 9 defects occult the incident light and create a reduction of the transmitted light received by the photodetector device, is also a process of continuous detection, since, during the control time, the photodetector device does not cease monitoring the ampoule.

In Patent Application FR-A-2 451 043, the photosensitive surface of the photodetector device is constituted by a plurality of small light receivers, aligned along a strip parallel to a generatrix of the ampoule.

In the other French Patent Application mentioned hereinabove, FR-A-2 390,709, the photosensitive surface of the photodetector device is divided into a multiplicity of microphotoreceiving regions, which are disposed in one or more columns parallel to the axis of the ampoule, with or without overlapping in the direction perpendicular to the axis of the ampoule in the latter case and, possibly in addition, in one or more lines parallel to the direction perpendicular to the axis of the ampoule, at the level of the projection of the bottom of the latter. On the photosensitive surface, composed of twenty to one hundred and twenty distinct elements, each measuring from 0.01 to 1 mm 2, the relative surface area of the microphotoreceiver is rendered variable as a function of the limits of detection. The field of control may be modified as a function of the size of the transparent recipient, by modifying the number of microphotoreceivers used by means of a selection circuit. A switch enables a more or less high 4 0 0 9 number of microphotoreeeivers, disposed in one or more vertical rows, to be used, whose vertical dimensions are a function of the dimensions of the largest ampoule to be controlled, and possibly also disposed in one or more hori5 zontal rows whose dimensions are a function of the largest width of the ampoules to be controlled, such horizontal row or rows being disposed so as to correspond to the base of the ampoules.

In these various embodiments, each photoreceiver element is constituted by a bundle of optical fibres terminating against a photoelectric converter element, such as a photo-diode, a photo-transistor or any other appropriate photoelectric cell, connected to at least one amplifier which is specific thereto, in an analog circuit for particle detection, comprising a eapaeitor, eliminating the continuous component of the signal, and a threshold comparator of which the threshold corresponds to a standard reference value previously fixed and set for the level of detection of the foreign particles. An OR circuit then gathers together the signals coming from the different threshold comparators, and controls elimination of the ampoule if one of the latter delivers a threshold overstep signal.

At best, the surface monitored by these known devices corresponds to a zone of control in the form of an upturned T, of which one bar, parallel to the axis of the ampoule, coresponds to a generatrix or to a thin strip on the ampoule, of width much less than that of the ampoule, and of which the other bar, perpendicular to the axis of the ampoule, corresponds to a thin horizontal strip against the base of the ampoule, of which it covers the diameter, and of height much less than that of the liquid in the ampoule.

These devices do not enable the reliability required in the control of pharmaceutical products to be attained, as the monitoring limited to a very small proportion of the apparent surface of the liquid, and generally to a more or less wide generatrix remaining fixed but always much less than the width of the ampoule, makes it difficult to oontrol marked or printed ampoules. In fact, it often happens that the mark printed on the ampoule occults an important fraction of the small zone monitored, and that a particle in suspension cannot be detected. Moreover, the quantity of light deflected to the receiver or occulted depends on the position and the orientation of each particle in the recipient. Thus the probability of detection of the particle through a narrow generatrix decreases substantially.

US Patents Nos. 3 777 169 and 3 598 907 disclose Pq employing a process of detection consisting in comparing two successive images of an ampoule illuminated on a black background (the image being produced only by the light diffracted, reflected or deflected from the impurities in a direction substantially perpendicular to the illumination) ->5 produced analogically by means of a scanning camera. Only the light dots producing an analog voltage higher than a 4ϋ0θ β certain threshold are taken into account. Said voltage is then shaped in a square or rectangular signal (false digitalization which is independant of the value by which the threshold is overstepped. A substraction of two succes5 sive images, if it is not zero, signifies the presence of an impurity. One of the major drawbacks of this technique, in addition to those inherent in the technique of scanning, resides in the presence of a threshold which filters the reception before the processing of the signal proper. The role if this threshold is to eliminate noise but, as shown in US Patent No. 3 777 169, the useful signals are often of the same order of magnitude as the noise itself. It is then recommended to vary this threshold between the first and the second image, in order to avoid noise and parasitic variations.

It is an object of the present invention to overcome the drawbacks presented by the known control devices and processes, and to allow detection which is disturbed neither by a mark printed on the recipient nor by a defect in the recipient itself, so that the recipients containing at least one undesirable particle in a liquid contained therein can be sorted automatically, rapidly and reliably.

To this end, the invention firstly provides a process for detecting foreign bodies considered inadmissable, in particular solids, in a liquid contained in one or more recipients transparent to a certain light, said process comprising a detection which takes place when the recipient or recipients is/are motionless, and in which: i) The liquid is put into motion and illuminated by a beam of said light so that its image, produced by reflection, diffraction or refraction at approximately 90° relative to the axis of the light beam corresponding approximately to the light signals issuing from the entire visible surface of the liquid, is formed on a photosensitive surface, ii) at a first instant, a first image of this surface is analysed point by point, then iii) the results of this analysis are memorized; iv) at a second instant, a second image is analysed point by point, then v) the results of the second analysis are subtracted from those of the first, and finally vi) the result of the subtraction in v) is compared with at least one predetermined significant threshold of said foreign bodies, the analysis in stages ii) and iv) consists of measuring the representative magnitude of each of the said signals point by point, stage iii) consists of memorizing the magnitude of each of said signals, stage v) consists of subtracting, point by point, the magnitude of one of the signals from the second analysis from that of the corresponding signal from the first analysis, 5400θ thus obtaining difference signals, and stage vi) consists of comparing each of the said difference signals with the predetermined significant threshold of said foreign bodies.

Advantageously, at previously selected intervals of time, which may for example be of the order of 20 ms, one may memorize the results of the second analysis and repeat the process for a series of image pairs taken at the first and second instants already selected, one of the images being associable with several other images to form different pairs.

Due to the process according to the invention, the defects connected with the manufacture of the recipient and/or the existence of a mark thereon are not retained, when comparing two successive images, as they produce the same light signal, at the same precisely located spots on each of the two images.

A particle circulating in the liguid contained in the recipient analyzed is therefore detected reliably, such detection being based on the differences in light signals created by the or each particle circulating in thie liguid, which difference may in addition be known quantitatively. li It should be noted that the or each light signal threshold may be selected during a previous standardization operation, consisting in examining recipients containing defects serving as standards according to the reference system for controlling a liquid contained in a recipient transparent to the mode of detection, forming the subject matter oi French Patent Application FR-A-2 486 241.

According to another feature of the invention, the value of the electrical signal provoked by the passage of the image of the same defect on the sensitive surface being a function of its time of passage, whieh increases when the rotation of the liquid slows down, the value of the or each threshold significant of comparison varies as a function of time, to take into account the slowing down of the movement of the liquid in the recipient, and to obtain a substantially constant threshold of detection of the inadmissible foreign bodies.

The variation of the or each threshold significant of comparison is preferably controlled at predetermined intervals of time and is effected according to increasing values of such threshold or thresholds.

It is well known that the rotation of the liquid contained in the recipient may bring about a phenomenon of vortex or an instability of the surface of separation between the liquid and the air. These phenomena cause variable light signals which must not be interpreted as defects. To this end, and according to a further feature of the invention, the comparisons in two's of the successive images are effected on zones increasing from the image of the bottom of the recipient towards the image of the surface of the liquid, so as not to include the afore-mentioned vortex or instability. This measure enables control of the recipient to be started very soon after blocking thereof.

According to a further feature of the invention, a plurality of adjacent recipients are controlled simultaneously and the location, on the sensitive surface, of at least one zone in which the result of the substraction in two's is greater than said pre-established threshold, controls the emission of at least one signal for identifying the or each recipient in question for elimination thereof.

The invention also relates to a device for carrying out the process which has been described, which comprises: a system for putting into motion and subsequent immobilisation of the recipient or recipients, a light source delivering a beam of light to illuminate the recipient or recipients, 2Q a detecting assembly comprising a lens and a photosensitive surface in which assembly the axis of the beam of light illuminating the recipient or recipients is approximately perpendicular to the optical axis of the detecting assembly, the light signals which come from the visible surface of the recipient or recipients, illuminated by the beam of light, touching the photosensitive surface and thus forming an image point by point of the visible surface of the liquid on said photosensitive surface, tar a memory for memorizing the data relative to the image taken at a particular instant, a first comparing element showing the memorized data of the image taken at one instant and the data of an image taken at another instant by subtraction, and a second comparing element comparing the result of the subtraction with at least one predetermined threshold significant for said foreign bodies, the photosensitive surface comprising a plurality of microphotoreceptors in the form of a matrix of adjacent receiver and read cells, which are mechanically and electrically delimited, and which are excitable and readable independently of one another, the surface of the matrix being above the image of the visible surface of the liquid contained in the recipient or recipients, which surface is defined by the width of the recipient or assembly of recipients and the height of the liquid in said recipient or recipients, said matrix comprising an integrated electronic circuit, the output of which is connnected by a serial analog channel to the input of an analog-to-digital converter, the output of which is connnected to the input of the memory, the minimum capacity of which corresponds to the capacity required for memorizing the magnitude of said signals point by 40 09 point, corresponding to said image taken at one instant, and the first comparing element shows by subtraction the difference between the magnitude of said signals taken in pairs and belonging to the two images formed at said two different instants, and of which at least the first has been memorized and used as a reference, and the second comparing element compares said differences with the above predetermined threshold or thresholds.

Still according to the invention, the integrated circuit comprising the matrix of the photodetectors and its auxiliary transfer and control circuits may comprise other devices such as for example an analog-digital converter; in this case, the output is composed of a plurality of channels, one per bit of resolution of the converter and one per control or synchronisation channel. The first comparison member is preferably a subtractor of which the output is connected to the input of the second comparison member, in the form of a threshold comparator, delivering a threshold overstepping signal to a general control member and receiving at least one digital threshold value from the latter, which simultaneously ensures synchronization of the subtractor, the analog-digital converter and 54()09 the threshold detector, and delivers on the one hand to the memory, signals controlling memorization and signals controlling read-out of the memory, and on the other hand to the mechanism for sorting the recipients, a switching order for each recipient controlled.

Moreover, the general control member also ensures synchronization of a member for controlling and shaping the signals useful for the matrix of photosensitive cells.

Moreover, a variable gain analog amplifier is inter10 posed between the output of the matrix of photosensitive cells and the input of the analog-digital converter, the variation of the gain being obtained by digital control, at predetermined intervals, from the general control member, so that the gain decreases from the immobilization of the or each recipient to be controlled. This variation of the gain may be controlled at intervals of time chosen experimentally and the variable gain analog amplifier makes it possible to respect the detection threshold fixed by the prior adjustment of the device with recipients containing standard defects, as mentioned hereinbefore.

In a preferred embodiment, the general control member of the device is a microprocessor also connected to a second memory, containing the general programs ensuring the train of the sequences of operation and making it possible to obtain the series of successive images, the memorizations and comparisons of the images taken in two's ; to an input member of the particular programs, enabling in particular iG digital values of the comparison thresholds and digital control of the variable gain to be obtained ; to a control console ; to a printer recording the conditions of control and the results ; and finally to the mechanism for gripping and handling the recipients, to which the microprocessor delivers a mechanical order sequencing signal. The microprocessor may also control one or more other microprocessors to which it delegates certain tasks, such as for example the control of the subtractor member, the comparison with the threshold(s), the synchronization of the analog-digital converter.

In a preferred embodiment, the matrix of photosensitive cells of the device according to the invention is constituted by the sensitive surface of a charge-transfer televi15 sion camera, comprising for example 144 lines of 208 elementary photosensitive cells integrated on a silicon chip, which also comprises control, transfer and output circuits.

The or each controlled recipient may be illuminated axially or laterally and the matrix of photosensitive cells, whose optical axis is substantially perpendicular to the axis of the or each recipient, receives the image of the apparent surface of the liquid formed by a lens receiving the light reflected, diffracted, refracted or attenuated by the contents and the walls of the or each recipient.

If need be, in order not to deteriorate the quality of the pharmaceutical product contained in the recipients, an ultraviolet filter may be disposed between the source of light and the or each recipient.

If need be, an anti-dazzle filter, eliminating the wave lengths which may be detrimental to the quality of detection, taking into account the nature of the material used for the markings of the recipients, may be disposed before or after the recipients. Similarly, a filter placed between the recipient to be controlled and the source limits undesirable overheating by eliminating the useless infrared wave lengths.

Furthermore, a bundle of optical fibres may be used 10 for conducting the light from the source up to the vicinity of the or each recipient.

By using the device according to the invention, a plurality of recipients are preferably controlled simultaneously. If one of such recipients contains a foreign body considered as being inadmissible, a signal is emitted further to the comparison of two successive images memorized, and this signal, comprising the identification of the recipient to be rejected by localization on the sensitive surface of the camera, is processed by the microprocessor 2o which controls elimination of the recipient which has been judged defective.

The process and device according to the invention therefore use a method of detection by reflection and diffraction, so that the foreign bodies in the liquid produce an increase in light received by the photosensitive surface. To make the latter, a sensitive camera surface is used, constituted by an integrated circuit comprising a large number of elementary cells (for example 30000), which are, however, each well defined geometrically, and the output signals from these cells all pass via the same channel, which amplifies, digitalizes and memorizes the signals received.

It is to be noted that each elementary cell, being mechanically delimited definitely and stably, is well identified and the light received is digitalized (for example between 0 and 255). This digitalization which is systematic, permits to proceed with memorizing without error or instability and the subsequent comparisons are more accurate. The digitalized images are then compared in two’s so that the monitoring is quasi continuous but nevertheless made in a digital manner. The principle of detection is that it suffices that the difference between the same point of two successive images be greater than a certain threshold value, which may be variable as a function of the time, to control elimination of the controlled recipient. It is therefore a difference between two signals delivered from the same point which is demonstrated, which is very different as the signal received by each point of each image either oversteps a fixed threshold, or does not, in absolute manner. Moreover, the very large number of cells of the photosensitive surface enables several recipients to be controlled simultaneously, whilst taking into account almost the whole of the apparent surface of the liquid contained by each. Finally, the method of detection by reflection and diffraction simultaneously procures the advantage that it is 4 0 0 9 also possible to control the level of filling of the recipients, by detecting the position of the surface of separation between the liquid and the air, which constitues a zone of extreme brilliance over the whole width of the liquid contained in the recipient.

The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which : The single Figure symbolically shows the device used 10 for carrying out the process according to the invention.

The device shown symbolically in the single Figure comprises a source of light 1, illuminating axially and from underneath a group of five adjacent bottles 2 to be controlled, made of a material transparent to the light of source 1, and containing an injectable pharmaceutical product in which there are possibly some particles in suspension.

The source of light 1 may comprise a low-voltage quartz/halogen lamp, a reflector and, if need be, an optical PO system for concentration. A bundle of optical fibres 3 conducts the incident light from the source 1 up to the immediate vicinity of the bottom of the bottles 2, and if necessary a filter 4 against UV Rays is disposed between the source·1 and these bottles 2 in order not to deteriorate the injectable product, if necessary. An optical system for rendering pseudo cylindrical the beam of light inside the bottle and a diaphragm (neither being shown) reducing the luminous section in the inner diameter of the bottles 2 may also be provided between the bundle of optical fibres 3 and these bottles 2 in order to diminish the lighting of printings and defects in the bottles 2.

The light reflected and diffracted by the bottles 2 and their contents (liquid and particles in suspension) is filtered by an anti-dazzle filter 5, eliminating the wave lengths which may be detrimental to the quality of detection, taking into account the nature of the material or materials used for making the markings or inscriptions on the bottles 2, and the image of these bottles 2 is formed on a photosensitive surface 6 by a lens 7, suitably chosen taking into account the desired magnification, the distance between the bottles 2 and the photosensitive surface 6, and the luminosity, in accordance with the rules of the art.

The surface 6 is constituted by the sensitive surface of a charge-transfer television camera, made in the form of an integrated opto-electronic circuit. This sensitive surface is in the form of a matrix of adjacent elementary reception and read cells which are physically and mechanically defined and fixed with respect to one another, and capable of being excited independently of one another. This matrix is constituted by 1144 lines of 208 elementary photosensitive cells, or a total of 29 952 cells, of which each is in rectangular form and measures 30 microns in length and 28 microns in width, which represents a surface area of 84 x 10"5 mm 2. 4 0 0 9 This photosensitive surface 6, which may count 30 000 cells, or more, therefore receives the image of all, or virtually the whole of the apparent surface of the liquid contained in each of the five bottles 2, this apparent surface being defined by the width of a bottle 2 and the height of the liquid which it contains. About 3000 cells of the surface 6 are thus used for receiving the image of one bottle and for controlling the apparent surface of the liquid that it contains.

These cells allow the scanning, point by point, of this apparent surface of the liquid, whilst the content of the bottle is set into motion in the immobile bottle, due to the vortical motion given to the liquid by previously rotating then suddenly stopping the bottle 2, by means of a mechani15 oal device for gripping and manoeuvring the bottles (not shown), ensuring transfer, rotation and, at the end of control, sorting thereof.

The integrated circuit comprising the photosensitive surface 6 and its interior auxiliary circuits, is connected 2o by a single serial analog output 8 to the input of a variable gain analog amplifier 9, whose role will be explained hereinbelow, and itself connected by its output to the input of an analog-digital converter 10. The latter supplies a memory 11 whose minimum capacity is, in this example, two images of a group of five bottles 2.

At an initial Τθ, determined by a microprocessor 12 constituting a general control member of the device, and transmitted by a synchronization line 13 to a member 14 for controlling and shaping the signals useful for the integrated circuit of surface 6, the assembly of the cells of this latter point by point analysis, the image of the apparent surface of bottles 2, and the light signal received by each elementary cell is memorized at 11, after amplification at 9 and numeration at 10 (its numeration will for example be a number included between 0 and 255 depending on the nature of the signal). In this way, a first reference image is constituted.

At a subsequent instant T-|, the same surface is again analyzed and the light signal received by each elementary cell is again memorized at 11, in the same way, to constitute a second image.

The two images obtained at instants To and T-, are then compared point by point by a subtractor 15, connected to the output of the memory 11, which receives from the microprocessor 12 its respective input and output control orders via control lines 16 and 17, whilst the analog-digital converter 10 and the subtraotor 15 are respectively controlled from the microprocessor 12 via synchronization lines 18 and 19Similarly, fresh images are memorized in pairs, at instants Tn and Tn+1, at previously chosen intervals of time which may for example be of the order of 20 ms, then again compared. According to the invention, images of instants Tn+1, Tn+2 — may be compared with the image of Tn which is 4 0 0 9 taken as reference. It is not necessary to memorize images which are not used as reference. From the output of the converter analog/digital, said images may be compared directly with the memorized reference. The signals corre5 sponding to the possible differences, bearing witness to the presence of particles in the liquid, are transmitted via line 20 from the output of subtractor 15 to the input of a threshold comparator 21.

It is clear that defects in the bottles made at manu10 facture or defects due to the presence of a marking on the bottles, which are fixed defects, produce the same light signal at the same spots precisely located on each image. A comparison of these two images therefore reveals no difference, and these defects are not retained.

On the other hand, a particle circulating in the liquid contained in one of the controlled bottles is reliably detected, due to the differences in light signals created by this particle and presented by each successive image.

In order that only foreign bodies or solid particles considered as being inadmissible as their size is greater than a certain limit, be detected, a threshold significant of comparison, corresponding to a threshold significant of pinpoint light signal difference, is chosen in the course of a previous standardization operation, consisting in the examination of bottles identical to those to be controlled, and containing standard defects, according to French Patent Application FR-A-2,486,241 relating to a 4 Ο Ο 9 reference system for controlling a liquid contained in a recipient transparent to the mode of detection.

The numerical value of the chosen threshold significant of comparison is transmitted from the microprocessor 12 to the threshold comparator 21 via line 22, and a threshold overstep signal is delivered nt the output of the comparator 21 and transmitted to the microprocessor 12 via line 23, if a difference signal at its input is greater than the threshold.

The device therefore ensures comparison of the differences between the signals of two successive images with the threshold chosen.

Simultaneously, the processing of the signals received by the microprocessor 12 allows that or those of the zones of the photosensitive surface 6, each appropriated to the control of the image of the apparent surface of the liquid contained in a bottle, for which a difference at least between the pinpoint light signals memorized during the taking of the two successive images has proved greater than the threshold, to be located on said photosensitive surface 6.

Further to such location, the microprocessor 12 communicates, via a line 24, a switching order for each controlled bottle to a mechanical device for sorting the bottles on leaving the control device.

In synchronism, the microprocessor 12 also controls the mechanical device for gripping and handling the bottles 2, 4«»» which the control device comprises, to ensure motion of the bottles 2 on themselves and to develop the vortical motion of their contents, then the sudden immobilization thereof, and the corresponding orders are transmitted via a line 25 for sequencing the mechanical operations.

As the rotation of the contents of the bottles 2 therein may bring about a phenomenon of vortex or an instability of the surface of separation between the liquid and the air in each bottle 2, the photosensitive surface 6 may receive variable light signals which must not be interpreted as witnessing the presence of inadmissible particles in the liquid. To this end, the microprocessor 12 controls the member 14 for controlling and shaping the signals useful for the photosensitive surface 6, so that the zones of the photosensitive surface 6 increasing from that part of the latter receiving the image of the bottom of the bottles 2 towards the part receiving the image of the surface of the liquid in the bottles 2, are activated to allow pairs of successive images to be taken and then successively com20 pared, without including the image of the vortex or of the instability. This measure therefore enables the bottles 2 to be controlled very soon after they have been immobilized.

Moreover, as the rotation of the contents of the bottle 2 therein progressively slows down, the time of passage of the image of the same foreign body on an elementary cell of the matrix of the sensitive suface 6 increases. Now, the value of the electrical signal delivered by this elementary cell is, within certain limits, a function of this time of passage, therefore also the difference in two electrical signals delivered at successive instants. The detection device makes it possible to vary the value retained as significant difference between the electrical signals coming from each elementary cell, i.e. the threshold significant of comparison, as a function of time, in order to maintain constant the previously chosen level of detection.

This is obtained due to the microprocessor 12, communicating via line 22 a numerical value increasing in time from IQ the threshold significant of comparison to the threshold comparator 21. However to complete the action of this variation of the threshold significant of comparison, the microprocessor 12 controls via line 26 the variable gain analog amplifier 9. The value of the gain of this amplifier 9 is chosen by digital control, and its variation is controlled at intervals of time chosen experimentally, so that the gain takes values decreasing in time from the mechanical immobilization of.the bottles 2, following rotation thereof, and the amplifier 9 thus controlled makes 2o it possible to respect the level of detection fixed by the prior adjustment of the detection device by means of bottles containing standard defects.

When a vortex motion in the bottles 2 is much attenuated, and therefore when the activated zone of the photo25 sensitive surface 6 corresponds to the whole surface thereof, so as to control the whole image of the apparent surface of the liquid contained in the botles 2, the detection device also makes it possible to control the level of 4 0 0 9 filling of the bottles 2, by detecting the position of the surface of separation between the liquid and the air in each bottle 2, this surface of separation constituting a zone of considerable brilliance over the whole width of the liquid contained in the bottle 2.

The general programs ensuring the train of the sequences and making it possible in particular to obtain the start of the mechanical movements of the recipients, the successive shots, the memorizations and comparisons of images, are stored in a memory 27 connected to the microprocessor 12 to which is also connected a member 28 for entry of the particular programs such as a magnetic supports reader and recorder, allowing introduction of the values of the threshold significant of comparison of the comparator 21, the values of the gain of the amplifier 9, instructions relative to the selection of the increasing zones of the photosensitive surface 6, as a function of time, and to the selection of the maximum zone of the surface 6 activated as a function of the size and number of the bottles 2 to be controlled, etc...

Furthermore, it will be noted that the photosensitive surface may comprise a plurality of occulted cells of which the output signal, interpreted by the assembly processing logic, constitutes a black background reference allowing an overal correction of the device as a function of the deflections due in particular to temperature. 2S Finally, a control console 29 and a printer 30, recording the conditions and results of the controls, are connected to microprocessor 12.

The invention is not limited to the embodiment which has just been described. In a variant, to take into account the slowing down of rotation of the liquid in the bottles 2, the interval of time separating two memorized and compared images may be increased correlatively, so that the image of the or each undesirable particle has covered a distance greater than the dimensions of an elementary photoelectric cell.

Claims (13)

1. CLAIMS;

1. A process for detecting foreign bodies considered Inadmissable, in particular solids, in a liquid contained in one or more recipients transparent to a certain light, said process comprising a detection which takes place when the recipient or recipients is/are motionless, and in which: i) The liquid is put into motion and illuminated by a beam of said light so that its image, produced by reflection, diffraction or refraction at approximately 90° relative to the axis of the light beam corresponding approximately to the light signals issuing from the entire visible surface of the liquid, is formed on a photosensitive surface, ii) at a first instant, a first image of this surface is analysed point by point, then ill) the results of this analysis are memorized; iv) at a second instant, a second image is analysed point by point, then v) the results of the second analysis are subtracted from those of the first, and finally vi) the result of the subtraction in v) is compared with at least one predetermined significant threshold of said foreign bodies, the analysis in stages ii) and iv) consists of 5 4009 measuring the representative magnitude of each of the said signals point by point, stage iii) consists of memorizing the magnitude of each of said signals, stage v) consists of subtracting, point by point, the magnit5 ude of one of the signals from the second analysis from that of the corresponding signal from the first analysis thus obtaining difference signals, and stage vi) consists of comparing each of the said difference signals with the predetermined significant threshold of said foreign 10 bodies.

2. A process according to Claim 1, wherein the results of the second analysis are memorized between stages iv) and ν), and the process is repeated for a series of image pairs taken at the first and second instants already 15 selected, one of the images being associable with several other images to form different pairs.

3. A process according to Claim 1, wherein the threshold or thresholds vary as a function of time in order to take into account the slowing down of the movement of the 20 liquid in the recipient or recipients and to achieve a constant level of detection of said foreign bodies.

4. a process according to Claim 3, wherein the variation in the threshold or thresholds is controlled at predetermined time intervals according to the rising threshold value or values.

5. 5. a process according to Claim 2, wherein the images in the series of image pairs are formed on increasing zones corresponding initially to the base part of the recipient and increasing up to the surface of the liquid.

6. a process according to Claim 1, wherein the position10 ing on the photosensitive surface of at least one zone in which one of said difference signals exceeds the predetermined threshold controls the emission of at least one identification signal from the recipient or recipients to eliminate said recipient or recipients. 15 7. A device for detecting foreign bodies, in particular solids, in a liquid contained in one or more recipients transparent to a certain light, for implementing the process according to Claim 1, comprising: - a system for putting into motion and subsequent 20 immobilisation of the recipient or recipients, -a light source delivering a beam of light to ilium5 4009 inate the recipient or recipients, — a detecting assembly comprising a lens and a photosensitive surface in which assembly the axis of the beam of light illuminating the recipient or recipients is 5 approximately perpendicular to the optical axis of the detecting assembly, the light signals which come from the visible surface of the recipient or recipients, illuminated by the beam of light, touching the photosensitive surface and thus forming an image point by point of the

7. 10 visible surface of the liquid on said photosensitive surface, — a memory for memorizing the data relative to the image taken at a particular instant, — a first comparing element showing the memorized data 15 of the image taken at one instant and the data of an image taken at another instant by subtraction, — and a second comparing element comparing the result of the subtraction with at least one predetermined threshold significant for said foreign bodies, 20 — the photosensitive surface comprising a plurality of microphotoreceptors in the form of a matrix of adjacent receiver and read cells, which are mechanically and electrically delimited, and which are excitable and readable independently of one another, the surface of the matrix being above the image of the visible surface of the liquid contained in the recipient or recipients,which surface is defined by the width of the recipient or assembly of recipients and the height of the liquid in 5 said recipient or recipients, said matrix comprising an integrated electronic circuit, the output of which is connnected by a serial analog channel to the input of an analog-to-digital converter, the output of which is connnected to the input of the memory, the minimum 10 capacity of which corresponds to the capacity required for memorizing the magnitude of said signals point by point, corresponding to said image taken at one instant, and the first comparing element shows by subtraction the difference between the magnitude of said signals taken in 15 pairs and belonging to the two images formed at said two different instants, and of which at least the first has been memorized and used as a reference, and the second comparing element compares said differences with the above predetermined threshold or thresholds. 20 8. A device according to Claim 7, wherein the first comparing element is a subtractor, the output of which is connected to the input of the second comparing element in the form of a numerical threshold comparator delivering a 54309 threshold overshoot signal to a general control element and receiving at least one numerical threshold value from the latter, which simultaneously ensures the synchronization of a subtractor constituting the first comparing 5 element and the analog-to-digital converter, and, on the one-hand, delivers memory control signals and memory reading signals to the memory and, on the other hand, sends a switching instruction for each recipient checked to a recipient sorting mechanism. 10 9. A device according to Claim 8, wherein the general control element further ensures synchronization of a memory for controlling and forming the output signals of the matrix of photosensitive cells. 10. A device according to Claim 7, wherein a variable 15 gain analog amplifier is interposed between the output of the photosensitive cell matrix and the input of the analog-to-digital converter, the variation in gain being obtained by numeric control, at predetermined intervals, starting with the general control element, such that the 20 gain decreases with effect from the immobilisation of the recipient or recipients to be checked. 540 09

8. 11. A device according to Claim 8, wherein the general control element is a microprocessor connected to a second memory containing general programs ensuring the concatenation of the Operation sequences and enabling 5 the attainment of a series of successive images, storage and successive comparison of the magnitude of the signals corresponding to the images taken in pairs, an input element for special programs enabling in particular the acquisition of comparative numerical 10 threshold values and the digital control of variable gain, a control console, a printer for recording the control conditions and results, and 15 a mechanism for holding and manipulating the recipients, to which the microprocessor delivers a signal for the sequence of mechanical orders.

9. 12. A device according to Claim 8, wherein the matrix of photosensitive cells comprises the sensitive surface of a 20 charge-transfer television camera, said surface forming a part of the integrated opto-electronic circuit, which includes control, transfer and output elements. 3 3 540θθ

10. 13. A device according to Claim 8, which comprises an anti-dazzle filter disposed between the recipient and the photosensitive surface, thus eliminating the wave-lengths from the material or materials used to make inscriptions 5 on the recipient or recipients which would impair the quality of the detection.

11. 14. A device according to Claim 7, wherein the photosensitive surface comprises a plurality of occulted receptor cells furnishing a black background reference signal to 10 correct the deflections due to the variations in temperature.

12. 15. A process according to claim 1 for detecting foreign bodies, particularly solids, substantially as hereinbefore described with particular reference to and 15 as described in the accompanying drawing.

13. 16. A device according to Claim 7, substantially as hereinbefore described with particular reference to and as illustrated in the accompanying drawing.